Patent GB-218661-A (GB)
Title: Improvements in aerial systems for receiving radio signals
IPC: H01Q21/12
Filed: 1924-07-02
Abstract: 218,661. Soc. Franþaise Radio-Electrique. July 2, 1923, [Convention date]. Directive signalling.-A number of aerials such as 1, 2 and 3 are arranged in a straight line and coupled to a single receiving apparatus 8 by land lines such as 4, 5, 6. The relative strengths of the oscillations contributed by the various aerials are regulated by their heights and their closeness of coupling, and their phase relations depend not only on the direction of the radiation received but on the distances between the aerials, which are to be small compared with the wave length and the length and loading of the lines 4, 5, 6. These quantities are so adjusted as to obtain very high directivity with some sacrifice of intensity. In the known arrangement shown in Fig. 1 the amplitude of the oscillations due to the centre aerial 1 is double that of the oscillations due to each of the end aerials 2, 3, and the centre aerial is coupled in opposition to the other two, the effective lengths of the paths 4, 5, 6 being all equal. In this case the amplitude of the resultant oscillations is proportional to cos<2> @ where @ is the angle between the line of the aerials and the direction of the received radiation. In the arrangement according to the invention shown in Fig. 4 account has to be taken not only of the phase difference due to the distance apart, d, of the aerials but also of that due to the time taken to travel along the land line 7, and in this case the resultant amplitude is proportional to cos<4> @/2 . If five suitably coupled aerials be used, with effective heights calculated according to a method described in the Specification, the resultant amplitude will be proportional to cos<4> @ if the land lines are of equal effective length, or to cos<8> - if their effective lengths differ by amounts equivalent to the distances between the aerials. The polar diagram for the latter case is shown in Fig. 10. With larger odd numbers of suitably chosen aerials amplitudes proportional to higher even powers of cos @ or cos<2> @/2 can be obtained. When an even 2 number of aerials is used, the members of each pair being coupled in opposition to each other so as to be equivalent to a frame aerial and connected to the receiver either by land lines of unequal effective length or by coupling to a single land line as indicated in Fig. 16, the resultant amplitude obtained is proportional to cos<2n-1> 0 for <2>n aerials. In order to allow for the fact that propagation along land lines is somewhat slower than propagation through space, the detector may be connected at a point between the aerials at a distance x, Fig. 17, from the end aerial calculated from a formula given in the Specification. Pairs of aerials may be replaced by equivalent frame aerials. The Specification, as open to inspection under Sect. 91 (3) (a), comprises also an arrangement in which two lines of aerials at right angles are associated with a radiogoniometer so that the axis of the resulting polar diagram can be turned in any desired direction; or with several goniometers for the simultaneous reception of messages from several different directions, the aerials being in this case aperiodic. This subject-matter does not appear in the Specification as accepted.